The candidate has a background in clinical ophthalmology and ocular epidemiology, and proposes to extend his work and prevention of eye disease into the field of cataract prevention. This application outlines a three-phase training program in cataract-related clinical trials. In the first phase, class classroom training in the theory of clinical trials will be undertaken at the Center for Clinical Trials of the Johns Hopkins School of Public Health under Dr. Curtis Meinert. Courses in Biostatistics and Epidemiology will provide a theoretical framework for the remainder of the training. The second phase will involve practical training in clinical trials under the auspices of the Age-Related Eye Disease Study. (AREDS). AREDS is a randomized, controlled clinical trial designed to explore in prospective fashion the impact of anti-oxidants and other factors on the progression of age-related cataract. The candidate will be supervised by the Study Chairman, Dr. Frederick Ferris, in a program that will include participation in monthly meetings of the AREDS Study Operations Committee and annual meetings of the Data Monitoring Committee and AREDS Technical Group in Bethesda, participation in Quality Control Site Visits and other activities of the Coordinating Center, and analysis of study data. In the final phase of training, the candidate will design and execute a clinical trial, a follow-up on the Linxian Cataract Trials in China. These were the first randomized, controlled trials to demonstrate that supplementation with anti-oxidants could retard progression of cataract. The proposed study will take advantage of continued examination of this cohort, now aged 55 years and above, by the National Cancer Center Institute for cancer-related events, to obtain unique information on the long-term effects of anti-oxidant treatment on lens opacity over 15 years. This study will exploit the candidate's fluency in written and spoken Chinese. Dr. Sheila West will provide overall direction through the three phases of training.